WO03092657 relates to microparticles which are based on a biocompatible and biodegradable material. The surface thereof comprises cells of interest or fragments of same and in further comprise molecules of at least one active substance on the aforementioned cells or the environment thereof during the implantation of the microparticles, said molecules being released by the microparticles in a prolonged and controlled manner.
Cell therapy by grafting autologous or non-autologous precursor or mature cells is a promising strategy to repair diseased organs. Moreover, the recent development of stem cell biology has provided further excitement for cell-based therapy. Several teams have used embryonic stem cells, adult stem cells, tissue-derived stem cells or more recently induced pluripotent stem cells to repair injured tissues. In this context, adult stem cells and particularly mesenchymal stem cells (MSCs), also named multipotent mesenchymal stromal cells, appear as an attractive cell source for tissue engineering because of their safety, their relative accessibility from different tissues and the possibility of performing autografts. Indeed, these stem cells have been successfully used for musculoskeletal tissue engineering and regeneration applications due to their intrinsic property to differentiate. They are also able to differentiate into other cell lineages, such as neuron-like cells or endothelial-like cells, under specific conditions. Moreover, mesenchymal stem cells are known to be able to migrate to injured tissues and some of their reparative properties are mediated by paracrine mechanisms including their immunomodulatory actions. However, after transplantation the majority of the cells die or if previously induced toward a differentiated phenotype do not maintain this induced phenotype. Consequently due to the small cell number and a non-desired modification of its behavior the tissue repair process is not efficient and the cells do not integrate correctly the host environment. For an efficient use in therapy, cell engraftment needs to be ameliorated, that is particularly the short but also long-term survival and functional state of the cells after transplantation.
Growth and differentiating factors may improve survival and differentiation of the cells, and may also affect the immediate environment, thus allowing better graft integration. Various growth factors, cytokines or morphogens have been widely used for directing the differentiation of MSCs. Nevertheless, the administration of these factors still remains a technological challenge, due to their short half-life, pleiotropic actions and their limited passage through biological barriers. Therefore, the use of delivery carriers for these factors, such as nano or microdevices is now a crucial choice to both protect and allow a controlled and sustained release of for example a protein.
In addition to cytokines, several parameters including composition of extracellular matrix (ECM) and three-dimensionality of the microenvironment have been shown to strongly influence the survival and differentiation of human mesenchymal stem cells. In this regard, scaffolds providing the ECM surface have been developed for example for brain neuronal repair (Delcroix et al Biomaterials 2011).
Within this context, an attractive strategy is to provide these associated parameters within an implantable small-sized pharmacologically active scaffold conveying stem cells, thus stimulating transplanted stem cell engraftment by providing an appropriate microenvironment to the cells in vivo.
The present inventors directed their investigations to pharmacologically active microcarriers (Coated microspheres), which are biocompatible and biodegradable microspheres, engineered to preferably continuously release an active molecule and which present a cell adhesion surface of extracellular matrix molecules or cell adhesion molecules supplying a three-dimensional structure for the transported cells. These parameters combined in one small-sized microcarrier act on the transported cells and on the surrounding tissue. The proof of concept of this unique and simple device delivering cells and proteins has first been validated for neuroprotection and tissue repair for the treatment of neurological disorders using a neuronal cell line, neuronal precursors and adult stem cells combined to Coated microspheres with different cell adhesion surfaces (laminin, fibronectin, poly-D-lysine) and/or growth factors (NGF, GDNF, NT-3) (Tatard et al 2004, Tatard et al 2007, Delcroix et al 2011, Garbayo et al 2011). Furthermore, with the goal to provide an efficient support for cartilage repair, pharmacologically active microcarriers releasing transforming growth factor 3 (TGF-β3) associated to human mesenchymal stem cells were shown to induce their chondrogenic differentiation in vitro and in vivo [Bouffi C, et al. The role of pharmacologically active microcarriers releasing TGF-β3 in cartilage formation in vivo by mesenchymal stem cells. Biomaterials. 2010; 31:6485-931]. Nevertheless, these poly (D,L lactide-co-glycolide) (PLGA) pharmacologically active microcarriers released TGF-β3 in a low and incomplete manner (25% of bioactive protein in 30 days) due to protein-polymer interaction during the release period, leading to protein instability. Interactions are enhanced by the necessity of working at low encapsulation loadings in order to accurately deliver these highly active therapeutic proteins at physiological levels. In an attempt to circumvent this problem, hydrophilic segments poly(ethylene glycol) (PEG) were introduced into hydrophobic polyesters, like PLGA, forming triblock copolymer microspheres. The presence of PEG segments increase water uptake and therefore a higher protein release (TRAN et al. European Journal of Pharmaceutical Sciences 45 (2012) 128-137).
It is an object of the present invention to eliminate or at least to substantially mitigate said drawbacks of existing products and methods.